Former Republican U.S. Sen. Larry Craig aims to fend off a federal election lawsuit against him by arguing his infamous June 11, 2007, Minneapolis airport bathroom visit that ended in his sex-sting arrest was part of his official Senate business.

Craig is hoping to avoid repaying $217,000 in campaign funds the Federal Election Commission claims he misused to defend himself.

The FEC sued Craig in June in U.S. District Court in Washington, D.C., alleging he converted the campaign money to personal use by spending it on his legal defense after he was accused of soliciting sex in a Minneapolis-St. Paul International Airport bathroom. The commission argues Craig's defense had no connection to his campaign for federal office.

Craig counters that money tied to his airport bathroom trip was for neither personal use nor his campaign, but fell under his official, reimbursable duties as senator because he was traveling between Idaho and the nation's capital for work.

He cites a U.S. Senate rule in which reimbursable per diem expenses include all charges for meals, lodging, hotel fans, cleaning, pressing of clothing — and bathrooms.

"Not only was the trip itself constitutionally required, but Senate rules sanction reimbursement for any cost relating to a senator's use of a bathroom while on official travel," wrote Andrew Herman, Craig's lawyer in Washington, D.C., in documents filed Thursday.